The world woke on Wednesday to reports of a massive chemical weapons attack in the suburbs of Damascus, Syria. According to Syrian activists, hundreds of people -- maybe even more than 1,000 -- have died, gassed in their beds while they slept. Since the attack allegedly occurred in the middle of the night, the dead included women, children and infants. President Bashar Assad's crimes against his people have been barbaric from the beginning. But if these reports prove true, Aug. 21 will surely be the worst single day in the slow-burning massacre of innocence that has marked the past two years in Syria.

That's not because of the number of dead, or at least not because of the number alone. It is the way these people would have died -- in precisely the manner the United States and the international community once claimed they could not allow. It was one year and one day ago that President Barack Obama first said that Assad's use of chemical weapons against his own people would constitute a "red line" for the United States. He didn't just say it once. Obama repeated his warning to Assad at least four more times in the months that followed. He explicitly said the use of chemical weapons would be "a game-changer" for the United States.

Of course, not much about the game changed. Even after America's allies saw clear evidence of chemical weapons attacks, the White House needed more. And after the Obama administration announced it would begin arming Syria's rebels, it wasn't clear what those arms would entail, and more tellingly, that effort still hasn't begun. It's a safe bet that Obama will never refer to "red lines" again, because if he does, no one will know what he means.

The Obama administration isn't responsible for preventing this massacre in Syria. Obama cannot control what happens in Damascus or Cairo, and it's unfair to suggest otherwise. But he must also own the policies he creates and the messages those policies send. And here's the truth: The president will run out the clock on the problems he likes least. In Egypt, while Washington fretted over the definition of a "coup," the Gulf's monarchies happily stepped in to fill the void. In Syria, the administration hemmed and hawed about arming the rebels for 18 months. When they finally came around to the notion, the "good rebels" were buried in shallow graves. As it turns out, there is a cost to slow walking a foreign policy crisis.

We want our presidents to be judicious in how they exert American power abroad. Foreign policy is the one area where they act with a relatively free hand. If you doubt that, look at the supposed argument over whether former President Mohammed Morsi was ousted in a coup. Every high school civics student understands that Gen. Abdel-Fattah al-Sissi undemocratically removed Morsi from office. Congress passed a law that insists that any country whose democratically elected leader is deposed by the military can no longer receive military aid. Yet, for more than six weeks, the White House has simply sidestepped the matter and continued to support the Egyptian military. If that changes, it will only be because Egypt's generals have made it politically impossible to continue to support them, not because the White House feels bound by the Foreign Assistance Act.

The Middle East's autocrats understand how to turn a president's "judiciousness" into an effective weapon for murder. These strongmen -- be it Assad, el-Sissi, or a host of others -- recognize that when an American president demands proof, evidence good enough to stand up in court, to make foreign policy decisions, he is effectively turning a blind eye to their crimes. So, for every peaceful protester who is gunned down in Cairo, the regime gives us an armed mob of Muslim brothers. As Assad's death squads go from house to house, Damascus issues denials and counterclaims. If that's all it takes, then it is easy enough to create the fog of war, even when it's truly a massacre.

It's not that the Obama administration has failed to conduct the rudiments of diplomacy around these crises. Indeed, U.S. officials made their best-faith effort to try to persuade Egypt's generals to forestall the crackdown that began last week. But the generals proved to be shrewder negotiators. They calculated that they wouldn't pay a real price for defying the White House, and at least up until now, they are right. The Obama administration thought it was exerting leverage, while el-Sissi was playing rope-a-dope. Perhaps withholding aid would have caused el-Sissi to pause; we will never know. Doing so now will be purely reactive, a punitive measure after the fact; it won't prevent a massacre that's already being washed off the streets.

On Aug. 15, when Obama addressed the Egyptian military's assault on protesters, he spoke of the tension between America's interests and values. Indeed, he frequently elevates those geopolitical interests over our values. It's a welcome change after George W. Bush's administration, which lacked the caution and circumspection the job requires, especially in the first term. But there is more to the job than simply summing up risks and rewards, and the Obama administration has been far too slow to understand how its interests play out in Egypt. Obama may be one of our foremost realpolitik presidents, but you get the sense that he's just not very good at it.

So while his lawyers looked at the ways Egypt's coup could be defined as anything but what it was, el-Sissi plotted his bloody crackdown. While Obama's White House aides debated whether Syrian rebels were good guys or villains, Assad prepped his chemical stockpile and gradually put it to use. In the end, el-Sissi and Assad looked at Washington and came to the same conclusion: What might have once seemed like an audacious act was actually a smart gamble.

We will wait to see if the reports of the most recent Syrian atrocity can be verified, if there can be an accurate body count of how many died in the worst-reported use of chemical weapons since Saddam Hussein gassed the Kurds in 1988. An American intelligence official recently admitted to Foreign Policy that "as long as the Syrian regime keeps the body count at a certain level, we won't do anything." So perhaps the final body count will matter for the White House. The past two years, however, suggest it won't.

I used to think that, in the long run, when the memoirs are written and the minutes of the White House meetings are known, the 100,000 people who died in Syria would be one of the worst stains on this administration. Not because they failed to stop it, but because they failed to try. But I was wrong. One hundred thousand was the floor.

William J. Dobson is politics and foreign affairs editor of slate.com.